Cordless, powered surgical tool

ABSTRACT

A powered tool for performing surgical procedures. The tool includes a handpiece in which a power generating unit is housed. A control member is mounted to the handpiece. The control member is mounted to the handpiece so that the orientation of the control member can be selectively set relative to the point to which it is mounted to the handpiece and so it can move relative to a reference point on the handpiece. A control module monitors the orientation of the control member and its position relative to the reference point. Based on the control member orientation and position, the control module generates signals to regulate the operation of the power generating unit. When the power generating unit is a motor, the control module generates signals to ensure that the maximum speed at which the motor can be driven is less than the no load speed.

FIELD OF THE INVENTION

[0001] The invention of this application relates generally to acordless, battery operated powered surgical tool. More particularly, theinvention of this application relates to a cordless powered surgicaltool, such as a surgical saw, that can be selectively configured for thepreferences of individual surgeons and that is relatively quiet tooperate.

BACKGROUND OF THE INVENTION

[0002] The cordless powered surgical tool has become an importantinstrument for performing a number of different surgical procedures.Generally, this tool includes a handpiece in which an electricallydriven motor is housed. Power to energize the motor is supplied by abattery that is usually removably attached to the handpiece. A gearassembly and a coupling assembly transfer the rotary power developed bythe motor to a cutting accessory. Typically, the coupling assembly isdesigned to removably hold the cutting accessory to the rest of thetool. Generally these tools, like other tools are used for separatingand or removing hard and/or soft tissue from a patient.

[0003] A cordless powered surgical tool, as the name implies, does nothave a cord to serve as a power conduit from an external source. Thiseliminates the need for surgical personnel to concern themselves withsterilizing a cord so that it can enter a sterile surgical field duringa surgical procedure and/or ensuring that during a surgical procedure anunsterilized cord is not inadvertently brought into the surgical field.Another benefit a cordless surgical tool offers is that the eliminationof the cord result in the like elimination of the physical clutter andfield-of-view blockage the cord otherwise brings to a surgicalprocedure.

[0004] The Applicant's U.S. Pat. No. 5,747,953, CORDLESS, BATTERYOPERATED SURGICAL TOOL, issued May 5, 1998, and incorporated herein byreference, discloses a trigger assembly and control circuit suitable forintegration into a cordless surgical tool. The particular tool describedin this document is a drill. This type of tool has a linkage and acoupling assembly that are positioned to cause a drill bit to be drivenin a rotary motion. The trigger assembly disclosed in this patent hastwo triggers. Collectively, the trigger assembly and control circuit areconfigured so that depression of one trigger will cause the motor shaftto rotate in a first direction, arbitrarily, forward rotation.Depression of the second trigger will cause the motor shaft to rotate ina second direction, arbitrarily, reverse rotation. The trigger assemblyand control circuit are further configured so that simultaneousdepression of both triggers will result in current being supplied to themotor in such a pattern that it oscillates inforward-reverse-forward-reverse movement.

[0005] The assembly disclosed in U.S. Pat. No. 5,747,953 has provenquite useful in many powered surgical tools. It has proven especiallyuseful for integration in powered surgical tools that have tissueworking cutting accessories that are designed to rotate around theirlongitudinal axes. Accessories that are so driven include drill bits andwires which are driven by drills and/or wire drivers

[0006] However, there are limitations associated with other cordlesssurgical tools, specifically, saws. Generally, a powered surgical saw isa powered surgical tool with a linkage that causes the associatedcoupling assembly to move in a repetitive back-and-forth pattern. Thecoupling assembly holds a blade that is designed to cut tissue. Somesaws have a linkage assemblies designed to move the complementary sawblades back and forth in a reciprocating pattern, along the longitudinalaxes of the associated blades. Other saws have linkage assemblies thatmove the associated blades in a sagittal or oscillating movement,specifically so that the blades pivot back and forth.

[0007] One of these limitations is associated with the fact that, by thevery nature of its method of use, a saw blade engages in repetitive backand forth action. As a result of this motion, the blade is invariablyrepetitively forced against components of the coupling assembly thatholds the blade to the saw. Components forming the linkage assembly andcoupling assembly similarly repetitively contact each other as a resultof the bi-directional movement in which these components engage. Thiscomponent contact results in an appreciable amount of noise beinggenerated when a saw is actuated. This noise, at a minimum, can make itdifficult to hear other sounds in an operating room. This noise canfurther be distracting to the surgeon and serve as one of theenvironmental factors that contribute to the stress surgical personnelexperience when performing a procedure.

[0008] One means by which surgical personnel have tried to reduce thenoise developed by a saw or other powered surgical tool is to run thetool at less than its highest speed. Typically this is the free speed,the no load speed, of the motor integral with the tool. Typically, thisspeed control is performed by manually depressing the trigger integralwith the tool so that it is only partially depressed. Often a surgeonwill operate the tool in this manner in the short time period before theassociated cutting accessory is pressed against the tissue the accessoryis intended to work. Then, as the motor speed drops as a consequence ofthe motor developing torque, the surgeon will adjust the pressure placedon the trigger to maintain the operation of the motor at the desiredspeed. While this method has proven somewhat successful in reducingtool-generated noise, it requires the surgeon to concentrate on theextent he/she has depressed the trigger integral with the tool. Thus,the surgeon has to devote some attention to the trigger setting; thismay distract from the surgeon's ability to concentrate on other aspectsof performing the surgical procedure.

[0009] Another method some surgeons find useful in reducing tool noiseis to perform the surgical procedure with a slower speed tool. This typeof tool, in comparison to its higher speed counterpart, generates lessnoise. It should also be apparent that, in comparison to a high speedtool, the lower speed tool is less powerful and may not be able to cuttissue as fast. In some instances, the lower speed tool may not evenhave the power to perform the task that can be accomplished with thehigher speed tool. Consequently, in a facility where surgeons find alower speed tool useful, the facility typically also finds it desirable,if not necessary, to also have the higher speed tool available. Thislatter tool is thus present for use by surgeons that prefer its fasteroperation and do not object to the noise. It is also necessary to havethe higher speed tool ready for situations where it can perform tasksthat are difficult, if not impossible, to accomplish with the lowerspeed unit. This essentially requires the hospital or other surgicalfacility to, in a sense, double the number of tools it has available inorder to accommodate for the preferences of individual surgeons. Thisnear duplication adds to the expense associated with providing asurgical facility.

SUMMARY OF THE INVENTION

[0010] This invention relates to a cordless powered surgical tool with acontrol assembly that governs the initial operating speed of the tool soas to reduce the noise generated by the tool and the wear to which itscomponents are exposed. This invention also relates to a controlassembly for a surgical tool that has a trigger assembly that allows thesurgeon to easily select the maximum speed of the tool.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention is pointed out with particularity in the claims.The above and further features and benefits of the invention may bebetter understood by reference to the following description take inconjunction with the accompanying drawings in which:

[0012]FIG. 1 is a perspective view of a cordless powered surgical toolinto which the features of this invention are incorporated;

[0013]FIG. 2 is an exploded view of the tool of FIG. 1;

[0014]FIG. 3 is a diagrammatic and block diagram of the control circuitof the powered surgical tool of this invention;

[0015]FIGS. 4A and 4B are, respectively, exploded and cross-sectionalviews of the trigger assembly;

[0016]FIG. 5 is a perspective view of the proximal facing end of theshaft housing of the trigger assembly;

[0017]FIG. 6 is a perspective view of the proximal facing end of thetrigger and outer shaft of the trigger assembly;

[0018]FIGS. 7A and 7B are, respectively, top and exploded views of thecarriage assembly;

[0019]FIG. 8 is a graph depicting the speed torque curves of the poweredsurgical tool of this invention;

[0020]FIG. 9 is a schematic view of components integral with analternative control circuit of an alternative version of this invention;

[0021]FIG. 10 is a graph depicting alternative speed torque curves ofthis invention; and

[0022]FIG. 11 is a schematic and block diagram of an alternative sensorassembly of this invention.

DETAILED DESCRIPTION

[0023]FIGS. 1 and 2 illustrate the basic features of a powered surgicaltool 20 that is constructed in accordance with this invention. Tool 20is a sagittal saw. It should, of course be recognized that other toolssuch as reciprocating saws, drills, reamers and wire drivers may embodythe features of this invention. Tool 20 includes a housing 22 thatcontains most of the other components of the tool. Housing 22 has anupper portion 24 in which contains a DC driven, variable speed motor 26.A sagittal head 28 extends forward from an opening in the housing upperportion 24. Fitted to the sagittal head 28 are a linkage assembly 30 anda coupling assembly 32. The linkage assembly 30 is connected to theoutput shaft of the motor 26 and the coupling assembly 32. The linkageassembly 30 transfers and converts the rotary motion of the motor shaftto the coupling assembly so that the coupling assembly moves in anoscillatory pattern. The coupling assembly 32 is designed to releasablyhold a saw blade, not illustrated, so that the blade engages in a likeoscillatory motion with the coupling assembly.

[0024] Housing 22 is further formed to have a handgrip 34 that extendsbelow the upper portion 24. A battery 25, depicted in FIG. 3, forproviding an energization current to the motor 26 is removably attachedto the base of handgrip 34. A controller 36 regulates the actuation ofthe motor 26. Controller 36 includes a moveable trigger 38 that extendsforward from housing 22. Located inside the housing 22 immediately abovethe trigger 38 is a carriage assembly 40. Trigger 38, in addition tobeing slidable in and out of the housing 22, can also be rotatedrelative to the housing. Three magnets 42, 44 and 46 (FIG. 7A) aremoveably mounted to the carriage assembly 40. The trigger and carriageassemblies, 38 and 40, respectively, are connected so that depression ofthe trigger results in the displacement of two of the three magnets 42,44 and 46. Which two of the magnets are actuated is a function of therotational orientation of the trigger 38 relative to the housing 22.

[0025] More particularly, the housing 22 is formed so that the forwardfacing end of upper portion 24 is open. A face plate 47 is seated inthis opening. Face plate 47 is the structural member of the tool 20 towhich motor 26, sagittal head 28, trigger 38 and carriage assembly 40are mounted.

[0026] The control assembly 36 also includes a sealed module 48 locatedin the housing 22 above the carriage assembly 40. Internal to sealedmodule 48 is a control circuit for regulating the actuation of the motor26. This control circuit is generally described by reference to FIG. 3.In one version of the invention, the control circuit includes threesensors 53, 55 and 57. Each sensor is seated in the module 48 so as tobe located in the path of travel of a separate one of the magnets 42, 44and 46, respectively. Each sensor 53, 55 and 57 generates a signalrepresentative of the strength of the magnetic field generated by theassociated magnet 42, 44 and 46, respectively. In one version of theinvention, sensors 53, 55 and 57 are Hall effect sensors. The signalsgenerated by the sensors 53, 55 and 57 are applied to a motor regulator60, also part of the control circuit.

[0027] Motor regulator 60, based on the signals generated by the sensors53, 55 and 57, controls the application of current to the windingsintegral with motor 26 so as to regulate the actuation of the motor andthe speed with which the motor shaft rotates. Generally, it should beunderstood that sensor 53, the sensor associated with magnet 42generates a signal indicating whether or not the motor is to be actuatedso its shaft rotates in a first direction, arbitrarily for this purpose,being called the forward direction. Sensor 57, the sensor associatedwith magnet 46, the magnet furthest from magnet 42, generates a signalindicating whether or not the motor should be actuated so that the shaftrotates in a reverse direction opposite the forward direction. Sensor55, the sensor associated with center-located magnet 44, generates asignal indicating the speed at which the motor is to be driven. Based onthese signals, motor regulator 60 selectively applies current to thewindings of the motor so as to cause the rotation of the shaft in thedesired direction and at the desired speed.

[0028] Internal to the motor regulator 60, it should be understood thatthere is circuitry that comprises a speed regulator 61. The speedregulator 61 is connected to the motor 26 for monitoring the speed ofthe motor. In motors with sensors, for example, Hall sensors, the speedregulator 61 monitors the output signals generated by those sensors. Insensorless motors, speed regulator 61 is connected to the windings ofthe motor to monitor the back EMF pulses. A component internal to thespeed regulator 61 includes a tachometer for, in response to the signalsreceived from the motor, generating a signal representative of shaftspeed. The speed regulator 61 also includes some sort of comparator thatcompares the motor speed to the user-selected speed for the motor. Theoutput signal generated by the comparator is thus used by othercircuitry internal to the motor regulator 60 to cause current to beflowed to the motor at an appropriate rate to ensure that the motorshaft, to the extent possible, is rotated at the user selected speed.

[0029] A detailed discussion of the control circuit including both themotor regulator 60 and speed regulator 61 is found in U.S. Pat. No.5,747,953 which is incorporated herein by reference. Alternative circuitcomponents for the motor regulator are found in U.S. Pat. No. 6,025,683,MOTOR CONTROL CIRCUIT FOR REGULATING A DC MOTOR, issued Feb. 15, 2000and incorporated herein by reference.

[0030] As discussed above, the above motor regulator 60 is constructedto actuation the associated motor 26 in either a forward or reversedirection. The power tool 20 of the described version of the inventionis a saw. Linkage assembly 30 is capable of transferring the rotationalmoment of the motor shaft, regardless of the forward or reverse state ofthis moment into oscillatory motion. Therefore, for the purposes of thisparticular type of power tool constructed in accordance with thisinvention, the fact that the motor can be actuated so that its shaftrotates in either a forward or reverse direction is not relevant.

[0031] Trigger 38 is part of a trigger assembly 64 now described byinitial reference to FIGS. 4A and 4B. The trigger assembly 64 includes agenerally cylindrically shaped shaft housing 66, now described byreference to FIG. 5. Shaft housing 66 is closed at its proximal end andopen at its distal end. (“Proximal” shall be understood to be towardsthe end of the tool facing the surgeon; “distal” is understood to betowards the surgical site to which the tool is applied.) Shaft housing66 is further formed so as to have a flat, circumferentially extendinglip 68 that extends around the open distal end of the housing 66. Shafthousing 66 is the component of the trigger assembly 64 that isphysically mounted to the face plate 47. When the trigger assembly 64 isso mounted, lip 68 seats in a recess formed around a hole in the faceplate 47 in which the shaft housing 66 is seated. The shaft housing 66is further formed to have a forward section 70, the section from whichlip 68 extends, that has an outer diameter greater than the outerdiameter of the remaining, rearwardly extending main body of the housing66. Shaft housing forward section 70 is formed to have a radiallydirected threaded bore 72. Bore 72 is dimensioned to receive a fastener(not illustrated) that extends through the face plate 47 so as to holdshaft housing 66 to the face plate.

[0032] Shaft housing 66 is further formed to have a back face 74 thatcloses the proximal end of the housing. Back face 74 is formed with agenerally rectangularly shaped center opening 75. The back face isfurther formed to have four peripheral openings, 76, 78, 80 and 82 thatare located about the perimeter of the back face that are spaced 90°apart from each other. Openings 76-82, it will be observed, extend intothe circumferential side wall that forms the main body of the shafthousing 66.

[0033] Trigger 38 is formed to be the head end of an outer shaft 84, nowdescribed in detail by reference to FIG. 6. The main body of the outershaft 84 is generally tube-shaped so that it can be slidably fitted inshaft housing 66 and so that it can rotate in the housing 66. Theproximal end of the outer shaft is formed to have two diametricallyopposed legs 86 and 88. It will be observed that leg 88 is shorter thanleg 86. Extending forward of legs 86 and 88, it will be understood thatthe main body of outer shaft 84 is formed with a bore 90. Bore 90extends partially into trigger 38. Outer shaft 84 is dimensioned so asto be both seated in the shaft housing 66 and so that a forward sectionof the main body of the shaft as well as trigger 38 are located forwardof the shaft housing.

[0034] The outer shaft 84 is fitted over a generally solid, rod likeinner shaft 92 also located in shaft housing 66. Inner shaft 92 isshaped to have a stem 93 that is generally rectangularly shaped. Morespecifically, stem 93 is shaped to slidably extend through centeropening 75 of the shaft housing back face 74 without rotating. Washers87 and 89 are secured to the proximal end of stem 93, the end thatextends out of the shaft housing 66 by a threaded fastener 95. Fastener95 is threaded into a complementary bore 97 in the rearwardly directedface section of the inner shaft stem 93. Washer 87 and 89 aredimensioned to extend over opening 75 so as to prevent the forwardmovement of the inner shaft 92 out of the shaft housing 66.

[0035] Extending forward from stem section 93, inner shaft 92 has agenerally circular cross-sectional profile. This forward portion of theshaft 92 is formed with to define an annular groove 96 that is locatedimmediately forward of stem section 93. Groove 96 is dimensioned toaccommodate an O-ring 98.

[0036] A laterally extending multi-section bore 102 extends through theforward section of the inner shaft. Bore 102 is dimensioned to have amain section dimensioned to accommodate at coil spring 104. At one end,bore 102 has a reduced diameter such that the step between theindividual bore sections serves as a stop for one end of the spring. Atthe opposed end, bore 102 has a larger diameter. This larger diameterportion of the bore 102 is shaped to accommodate therein a ball bearing106. Immediately rearward of the distally-directed face of the innershaft 92, the shaft 92 is formed to have a groove 108 that extendsaround the outer circumference of the shaft. Groove 108 does notextended circumferentially around the outer surface of shaft 92.

[0037] When the trigger assembly 64 is assembled, the outer shaft 84 isseated in the inner shaft 92 so that that the forward portion of theinner shaft 92 seats in bore 90. A pin 110 is press fit in an opening111 in the trigger 38 and extends into bore 90. Pin 110 also seats ingroove 108. Pin 110 thus holds the trigger 38 and outer shaft 84 to theinner shaft 92. When the trigger assembly 64 is so assembled, ballbearing 106 seats against an inner wall of outer shaft 84 that definesbore 90. This inner wall is formed to define indentations 112 that are1800 apart from each other. While the inner shaft 92 cannot rotate,outer shaft 84 is capable of rotating relative to the inner shaft. Asthe outer shaft 84 so rotates, ball bearing 106 goes in and out ofregistration with the opposed indentations 112. The seating of the ballbearing in each of the indentations 112 provides tactile feedbackregarding the orientation of the trigger 38 for purposes to be explainedbelow.

[0038] Since groove 108 does not extend circumferentially around innershaft 92, the material forming the inner shaft blocks the rotation ofpin 110 and therefore the rotation of trigger 38 and outer shaft 84. Inone version of the invention, trigger assembly 64 is constructed so thatthe trigger 38 and outer shaft 84 can only rotate 1800. In order todetermine the rotational orientation of the trigger 38 to the handpiece,one end of the outer face of the trigger is formed with an orientationdimple 113.

[0039] A spring 114 is also disposed in shaft housing 66. Spring 114extends between the distally directed surface of shaft housing back face74 and the proximally directed surface of the inner shaft 92 adjacentthe distal end of stem 93. Spring 114 provides the biasing force thaturges the inner shaft 92, and therefore trigger 38 and outer shaft 84,distally, away from face plate 47. Collectively, the components of thetrigger assembly 64 are selected so that, absent any external contraryforce, spring 114 holds the shafts 84 and 92 in position so that theshaft legs 86 and 88 are wholly seated within shaft housing 66.

[0040] Trigger assembly 64 further includes an O-ring 116 that extendsaround the main body of the outer shaft 84. O-ring 116 is seated in anannular groove in the shaft housing forward section 70.

[0041] The trigger assembly 64 is further formed so that around the openend of the outer housing 66, the housing is formed with a counterbore118 that surrounds the main bore through which shafts 84 and 92 extend.A variable number of shims 120 are seated in counterbore 118 so as toextend around the shafts 84 and 92. Shims 120 are held in place by aring 122 that is press fit in the counterbore 118. Owing to the presenceof shims 120, ring 122 extends forward a slight distance in front of thedistally-directed surface of housing lip 68. Consequently, when trigger38 is pressed inwardly, towards tool housing 24, the inward movement ofthe trigger 38 and shafts 84 and 92 is thus limited by the abutment ofthe proximally directed surface of the trigger against the distallydirected surface of ring 122. The significance of this mechanical stopis discussed below.

[0042] Carriage assembly 40, the assembly to which magnets 42, 44 and 46are mounted, is now described by reference to FIGS. 7A and 7B. Thecarriage assembly includes a plastic, approximately H-shaped frame 126.Generally, frame 126 consists of a head end 128, a tail end 130 that isspaced from and extends generally parallel to the head end and a centerbeam 132 that connects the opposed ends. Screws, (not illustrated),extend forward from the distally directed face of frame head end 128 andseat in holes in the proximally directed surface of the face plate 47 soas to hold the carriage assembly to the face plate, (face plate holesnot illustrated). Pins 134 extend upwardly from frame head end 128. Thesubstrate to which sealed module 48 is mounted seats over pins 134.

[0043] Magnets 42, 44 and 46 are mounted in separate carriers 136, 138and 140, respectively. The carriers 136, 138 and 140 are themselvesslidably mounted to individual pins 142 that extend between the head andtail ends 128 and 130, respectively, of frame 126. More specifically,the distal end of each pin 142 is seated in a through hole 144 formed inthe frame head end 128. The proximal end of each pin 142 is fitted in anotch 143 formed in the frame tail end 130. The pin 142 to which thecenter carrier, carrier 138, is mounted is aligned with the longitudinalaxis of beam 132. The pins 142 to which carriers 136 and 140 are mountedare spaced laterally away from beam 132.

[0044] The pins 142 to which carriers 136 and 140 are mounted also aremounted to frame 126 so as to extend a slight distance forward of headend 128. The distal ends of these pins 142 seat in openings formed inface plate 47 to facilitate the stabilization of carriage assembly 40.

[0045] Carriers 136 and 140 are mirror images of each other. Eachcarrier 136 and 140 has a generally rectangularly shaped body 144 inwhich the associated magnet 42 or 46, respectively, is housed. Eachcarrier 136 and 140 also has an elongated sleeve 146 integral with thebody 144 that is located along one side of the body and extendslongitudinally. Sleeves 146 are the elements of carriers 136 and 140through which pins 142 extend. Each carrier 136 also has, on the sideclosest to frame beam 132 a diagonally downwardly extending leg 148 anda diagonally upwardly extending arm 150.

[0046] Carrier 138, the carrier in which magnet 44 is housed, is locatedwithin an elongated groove 154 formed in the frame center beam 132. Inthe illustrated version of the invention, carrier 138 actually containstwo magnets 43 and 45 that collectively comprise magnet 44. Thepolarities of the magnets 43 and 45 are reversed so that theycollectively produce a magnetic field that is relatively focused andintense. The carrier 138 includes an elongated body 156 in which themagnets 45 and 47 are seated. Feet 158 extend downwardly from theopposed ends of the body 156. Carrier feet 158 are formed with openings160 so that feet 158 can be fitted over the center located pin 142.

[0047] Springs 162 are fitted over pins 142. Each spring 162 extendsbetween the frame tail end 130 and the carrier 136, 138 or 140 mountedto the pin 142 with which the spring is associated. Springs 162 thusbias the carriers towards the frame head end 128 in the absence of anycounteracting force. As a consequence of this positioning, the leg 148of carrier 136 is normally seated in shaft housing bore 76; the leg 148of carrier 140 is normally seated in shaft housing bore 82.

[0048] Carriage assembly 40 is further configured so that the arms 150of both carriers 136 and 140 abut the distally directed surface ofproximal foot 158 of carrier 138. Thus, the proximal movement of eithercarrier 136 or 140 results in the like displacement of carrier 138.

[0049] A surgeon actuates the saw 10 of this invention by rotating thetrigger 38 so that the longitudinal axis of the trigger is aligned withthe longitudinal axis of the housing 24. The surgeon receives tactilefeedback that the trigger 38 and outer shaft 84 are so aligned by theseating of ball bearing 106 in one of the indentations 112. When thetrigger is so aligned and, more specifically when it is so aligned andthe orientation dimple 113 is in its closest position to the sagittalhead 28, output shaft leg 86 is aligned with housing shaft back facebore 76; shaft leg 88 is aligned with back face bore 78. When thetrigger 38 and outer shaft 84 are so positioned, pressure can be placedon the trigger to depress it rearwardly. The surgeon actuates the saw 10by applying finger pressure on the trigger 38 to urge the triggertowards the face plate 47. This movement results in the displacement ofshaft leg 86 rearwardly, out of the shaft housing 66 and against the leg148 of carrier 136. Thus, the rearward movement of the trigger 38, whenin this orientation, results in the like displacement of carrier 136and, therefore, also carrier 138. The rearward movement of magnets 42and 44 and 44 are detected by sensors 53 and 55. As a result of thechange of signal state from sensor 53, motor regulator 60 starts toapply signals to the motor so as to result in the eventual rotation ofthe motor in the forward direction.

[0050] The speed with which motor 26 is to be operated is based on thesignal from sensor 55. This signal is a function of the distance betweenmagnet 44 and sensor 55. Sensor 55, motor regulator 60 and speedregulator 61 are configured so that an output signal from the sensorindicating that the magnet 44 is relatively close is interpreted by theregulators as an indication the motor is to be operated at a relativelyhigh speed.

[0051] However, as discussed above, trigger 38 abuts ring 122 to preventthe complete depression of the trigger. This stoppage thus limits theextent to which magnet 44 is able to move towards sensor 55. The endconsequence of this restriction in movement of the trigger is that themaximum speed at which the motor regulator will allow the motor to runis less than its free speed, the no load speed. It should be understoodthat this “no-load speed” is the maximum speed for the handpiece motor26 based on the maximum voltage that can be supplied by battery 25. Forexample, in one particular version of this invention, it is anticipatedthat the motor may have a no load speed of between 15,000 and 30,000RPM. In this version of the invention, the saw 20 of this invention isconstructed so that when the trigger is aligned as described above, themaximum speed of the motor is between 30 and 70% of its no load speed.In more preferred versions the no load speed of the motor is between18,000 and 24,000 RPM and/or the limited maximum speed is between 40 and60% of the no load speed.

[0052] A consequence of this speed limiting of the motor 26 isunderstood by reference to FIG. 8. Typically, a tool is actuated so thatthe motor will run at the no-load speed and, then, the cutting accessorycoupled to the tool is pressed against tissue. The movement of themoving cutting accessory against tissue causes the motor to apply atorque to the accessory. Given that the energy available to actuate themotor is limited, the production of torque results in the immediateslowing of the speed at which the rotor shaft is able to turn asrepresented by dotted line segment 172.

[0053] However, the tool 20 of this invention is constructed to speedlimit the maximum speed of the motor. Thus, even when the tool 20 is notbeing used to produce torque, due to the limiting affect ring 122 has onthe displacement of trigger 38, the surgeon can only set to run themotor at a limited maximum speed (MAX SPD1 in FIG. 8), that is less thanthe no load speed. When the tool 20 is in this state, and thecomplementary cutting accessory is pressed against tissue, the motorwill produce torque as before. However, because the speed of the motoris less than the no load speed, the battery will, for the given powersetting, have power available to continue to energize the motor. Thus,the speed regulator 61 is able to apply energization signals to themotor 26 so that the motor is for some relatively low torqueapplications, able to run at the limited maximum speed, as representedby line segment 174. In other words, the speed regulator 61 providesclosed loop speed regulation of the motor based on the actual motorspeed, and the signal representative of user-selected speed even as theload applied to the motor 26 varies.

[0054] Eventually though, as the amount of torque the motor is requiredto produce increases, the motor speed will start to drop as representedby diagonal line segment 176.

[0055] Alternatively, the surgeon may, prior to using the tool 20,decide the tool does not have to be operated at a speed as high as MAXSPD1. If the surgeon makes this decision, prior to actuating the tool,he/she rotates trigger 38 and outer shaft 84 around inner shaft 92. Thisrotation is possible because pin 110 is able to rotate in the innershaft groove 108. The surgeon stops rotating the trigger 38 when it isoriented 180° from its initial rotation; the trigger is longitudinallyaligned with housing 24. Visual observation is obtained of the triggerorientation by the fact that trigger dimple 113 is spaced from thesagittal head 28.

[0056] When the trigger 38 and outer shaft 84 are so aligned, shaft leg88 is in registration with shaft housing back face bore 82; shaft leg 76is aligned with back face bore 80. The surgeon can depress the triggerto actuate the tool 20. It will be recalled though that shaft leg 88 isshorter than shaft leg 86. Consequently, the trigger 38 and shafts 84engage in some free travel before these components are depressed enoughthat leg 88 abuts and starts to displace carrier 140. The overalldistance the trigger 38 and the outer shaft 84 can be displaced isconstant regardless of the rotational position of these componentsrelative to the rest of the tool 20. Therefore, owing to the relativelyshort length of leg 88, when the trigger 38 is fully depressed, the leg88 will have displaced carrier 140 a shorter distance than the distanceleg 86 was able to displace carrier 136 when the trigger was similarlydepressed.

[0057] The minimal displacement of carrier 140 results in magnet 46being placed in sufficient proximity to sensor 57 so that the sensorundergoes the state change required to cause the actuation of the toolmotor 26. However, the limited displacement of carrier 140 results in alike reduced displacement of carrier 138 and magnet 44. The limiteddisplacement of magnet 44 is monitored by sensor 55. The sensor 55therefore only produces an output signal to cause the motor regulator torun the motor at a limited maximum speed that is even less than themaximum speed for the tool when in the high speed setting, MAX SPD2 inFIG. 8. In the disclosed version of the invention, the motor shaft, whenactuated based on the detected displacement of magnet 44, will rotate inwhat can be considered the reverse direction. However, for the reasonsset forth above, this does not affect the back-and-forth movement ofblade 31.

[0058] Thus, tool 20 of this invention is constructed so that whentrigger 38 is fully depressed, the motor 26 will be actuated at amaximum speed that is less than the motor no load speed. As aconsequence of this reduced speed maximum speed operation of the motor,the frequency with which linkage assembly 30, coupling head 32 and theattached cutting accessory oscillate back and forth is likewise reduced.One benefit of this reduced oscillation is that less noise is generatedby the saw and cutting accessory as a result of its maximum speedoperation. A second benefit of this reduced oscillation is that the wearof the components that engage in this motion is likewise reduced. Thiswear reduction serves to increase the lifetime of these components.

[0059] While the maximum speed of the saw is reduced, this reductiondoes not adversely affect the saw's efficiency for performing a surgicalprocedure. This is because when the saw is running at the maximum speedand the cutting accessory is applied to a surface and torque isproduced, the speed regulator causes additional power to be supplied tothe motor so as to maintain the speed. Thus, the power tool will applythe same cutting power supplied by other tools but when a no load stateis less noisy.

[0060] Another feature of the power tool of this invention is that bythe simple rotation of trigger 38, the maximum speed of the tool can beset to a relatively high limit or a relatively low limit. Thus, in asituation in which the surgeon does not require high speed operation ofthe tool and would prefer quieter operation, the trigger can be set tocause the motor to run at a relatively low maximum speed. An additionaladvantage for operating the motor at a lower speed is noted bydot-and-dash line segment 175 of FIG. 8. Since the maximum speed of themotor is reduced in comparison to MAX SPD1, the amount of torque themotor will be able to develop before the surgeon notices an appreciablespeed drop off increases.

[0061] Alternatively, where a surgeon would prefer or require higherspeed operation, the trigger is easily reset so that, when the triggeris fully depressed the motor will run at a higher maximum speed. Thus,the single tool of this invention eliminates the need that sometimesarises to provide two similar powered tools that only vary in themaximum speed of their motors.

[0062] In the above-described version of the invention, as part of theassembly of tool 20, shims 120 are placed in face plate counterbore 66.More specifically, the appropriate number of shims 120 are fitted in thecounterbore 66 so that ring 122 extends forward of the face plate 47 asufficient extent to cause the appropriate limiting of triggerdisplacement that, in turn, will result in the motor being caused tooperate at the desired limited maximum speed.

[0063]FIG. 9 is a schematic diagram of an analog circuit that can beemployed as a speed limiting and maximum speed select circuit of thisinvention. In this version of the invention, the voltage present at theoutput of sensor 55, the Hall effect sensor, is the signalrepresentative of the user desired speed. This voltage is attenuated byapplication to a voltage divider before being applied to the motorregulator 60 and speed regulator 61. Specifically, two resistors 178 and182 are series-connected to the emitter of sensor 55. Two diodes, 180and 181 are series-connected between resistors 178 and 182. (A switch187 is located between resistor 178 and diode 180. The purpose of thisswitch 187, which should normally simply be considered closed, isdiscussed below.) The free end of resistor 182, the end furthest fromsensor 55, is connected to the collector of sensor 53 through a thirdresistor 184 and a forward biased diode 185. The same end of theresistor 182 is also tied to the collector of sensor 57 through aforward biased diode 186. The emitters of sensors 53 and 57 are bothtied to ground.

[0064] The voltage present at the junction of resistors 178 and diode180 is the signal applied to the motor regulator and speed regulator asthe signal representative of the user desired speed.

[0065] The trigger assembly with which this version of the invention isemployed does not have the mechanical stop, shims 120 and ring 122, ofthe first described version of the invention. Also, in this version ofthe invention, the outer shaft is designed so that shaft legs 86 and 88are of identical length. Thus, in this version of the invention,regardless of the relative orientation of trigger 38, when the triggeris depressed, the center magnet 44 is displaced the same amount.

[0066] In this version of the invention, when the trigger 38 is set tothe highest maximum speed orientation, magnet 42 moves towards sensor53; magnet 46 is not similarly displaced. As a result of thisdisplacement, only sensor 53 undergoes a state transition. Specificallyas a result of this transition, sensor 53 closes so as to tie the seriescircuit of resistors 178, 182 and 184 to ground. As a result of thiscircuit being tied to ground, the voltage present at the junction ofresistor 178 and diode 182, which is less than and proportional to theoutput signal from sensor 55, is the voltage applied to the motorregulator and speed regulator 60 and 61, respectively. Since thisvoltage will always be less than the maximum voltage output from sensor55, even when trigger 38 is fully depressed, the speed regulator willalways cause the motor to run at a limited maximum speed that is lessthan the no-load speed.

[0067] Alternatively, trigger 38 may be oriented to cause the motor torun in the low limited maximum speed state. When the trigger is thendepressed, magnet 46, not magnet 42, is the magnet that is similarlydisplaced. As a consequence of this movement, sensor 57, not sensor 53,undergoes the open-to-closed state transition. This state transitionties the series circuit of only resistors 178 and 182 to ground. Giventhe changes in the resistance of the sensor 55-to-ground voltagedivider, the voltage present at the junction of resistor 178 and 182 isless than the voltage present at this junction when magnet 44 undergoesa like displacement and trigger 38 is in the high speed maximum speedsetting. The reduction of this voltage causes speed regulator 61 to, inturn, actuate the motor so that it runs at the lesser of the two maximumspeeds.

[0068] An advantage of the foregoing version of the invention is thatone can set the maximum speed setting of the motor by the selection ofprecision resistors or the trimming of resistors. This eliminates theneed to have to select mechanical parts, such as shims and a nut, toserve as a mechanical stop. This version of the invention alsoeliminates the need to have precision shape the legs of the outer shaft84 so that when it is placed in the low speed maximum speed setting, thedesired lower maximum speed will be obtained.

[0069] Still another advantage of this version of the invention is thatin this version of the invention, when the trigger 38 is in the lowspeed maximum speed setting and is depressed, the motor 26 will start tobe actuated at the same point in travel as when in the high speedsetting. This eliminates the possibility that the surgeon will bemomentarily disconcerted due to the fact that, during the initialdisplacement of the trigger 38, the motor is not actuated.

[0070] Another advantage of the invention described with respect to FIG.9 is that the diodes 180, 181 and 185 or 186, compensate for signaldrift caused by temperature changes of the internal circuitry of thetool 20. In particular, the output signals of both sensor 55 and thetachometer internal to the speed regulator 61 tend to rise as a functionof the tool being relatively warm. Generally, there are two reasons thetool may be warm. First, as part of the process of sterilization of thetool 20, it is autoclaved. Sometimes, after the tool is autoclaved itmay be used before its temperatures cools to that of the ambientenvironment. Secondly, the heat generated by motor 26 may warm the othercomponents of the tool 20 to a level at which the output signals fromthe sensor 55 and tachometer start to drift. If the signals from thesecomponents drift, the voltage drops across the diodes 180, 181 and 185or 186 engage in a like drift in an opposite polarity. Thus, the diodescompensate for temperature induced variations in the signal present atthe output end of resistor 178 that would otherwise occur.

[0071] As mentioned briefly above, the above circuit may be providedwith some sort of switch or jumper, represented by switch 187, betweenresistor 178 and diode 180. This connection may be provided so that,during manufacturing, the circuitry connected between the switch 187 andground may be selectively installed or removed from the handpiece. Thus,a single subassembly can be provided that has the circuitry forperforming the speed limiting and limited maximum speed speed selectfeature of this invention or that does not include this feature.

[0072] It should be understood that the foregoing description isdirected to specific versions of the invention and that other versionsof the invention may vary from what has been described. For example,there is no requirement that any one of the features of this inventionbe solely incorporated into a powered surgical saw and/or solelyincorporated into a cordless tool. Thus, one or more features of thisinvention may be incorporated into an alternative powered surgical toolsuch as a drill or wire driver that is actuated by power supplied from aremote control console through a power cord. Similarly, it should berecognized that the saws that incorporate the features of this inventionneed not solely be saws that move the complementary blades in thesagittal motion. These features of this invention may readily beincorporated into saws that move their complementary blades inreciprocal motion.

[0073] Likewise, it should be understood that some powered surgicaltools of this invention may not employ electrically driven motors astheir power generating units. In these versions of the invention, thepower-generating unit may be such a device as a pneumatically drivenmotor, an ultrasonic surgical tool, a RF or electro cauterization probe,a laser or other heat or light emitting unit. The complementary couplingunit connects an accessory that transfers the energy developed by thepower-generating unit to the surgical site.

[0074] It should similarly be understood that not all surgical tools ofthis invention will incorporate both the maximum speed limiting assemblyand a limited maximum speed speed select trigger. Some tools of thisinvention may only be constructed to perform maximum speed limiting andnot be provided with a trigger that allows the surgeon to select thelimited maximum speed. Another alternative tool of this invention may beprovided with a trigger or other control member that can both by placedin a select orientation relative to the handpiece to which it isattached in order to provide an indication of maximum power the unittool should develop and that, in the selected orientation, be moveableto provide an indication of the amount of power the tool should, at anyinstant, develop. In some versions of this embodiment of the invention,the surgeon may only be able to set the tool to operate at a singlespeed, the set speed.

[0075] Similarly, while two speed limiting assemblies, one mechanicaland one electrical, have been described, it should be recognized thatalternative speed limiting assemblies may be incorporated into thepowered surgical tool 20 of this invention.

[0076] For example, shims may be placed in other locations to limit thetravel of trigger 38 and outer shaft 84. In one alternative version, forinstance, the shims are placed around the inner shaft stem 93. Theseshims are dimensioned to be fully enclosed within spring 114. Sufficientshims, as well as a lock nut, are provided around the stem so thatretraction of the outer shaft 84 and inner shaft 92 is stopped by theabutment of the proximal most shim, (or proximally positioned lock nut),abutting against the inner surface of shaft housing back face 74.Alternatively, the spring 114 may be fully compressible. In theseversions of the invention, shims placed at either end of the springlimit the extent to which trigger 38 can be rearwardly displaced.

[0077] Other mechanical maximum speed limiting assemblies of thisinvention may not even include shims. For example, an alternativemechanical speed limiting assembly may be provided by shaping leg 86 ofthe trigger assembly outer shaft 84 so that it does not immediatelydisplace carrier 136.

[0078] Alternatively, a mechanical speed limiting assembly may beconstructed by forming the outer shaft 84 so that it has a groove withtwo spaced apart longitudinally extending branches and a circumferentialsection that connects the branches. In this version of the invention,the shaft housing 66 has a pin that is seated in the groove. Thebranches of the grooves are positioned so that depending on whichposition the trigger 38 and outer shaft 84 are placed, one or the othergrooves is aligned with the pin. The length of the grooves is such thatthe pin abuts the end of the groove in which it is seated prior to whendepression of the trigger results in the complete retraction of theouter shaft. Thus, the pin and grooves function as mechanical stops thatlimit the displacement of the trigger so as to limit the maximum speedat which the motor 26 can be actuated. As a result of the grooves beingof unequal length, when the pin is in the longer groove, the tool can beactuated to run at the higher of the two maximum speeds; when the pin isin the shorter groove it can be actuated to run at the lower of the twomaximum speeds.

[0079] Alternative electronic speed limiting/maximum speed settingassemblies of this invention can be provided. In one version of theinvention, for example, the analog signal from the center sensor, sensor44, the speed sensor, is digitized. In this version of the invention,the maximum speed is determined based on which of the two maximum speedselect sensors, sensor 53 or 57, undergoes a state transition. If thehigher speed maximum speed select sensor, sensor 53, undergoes the statetransition, a logic circuit internal to the speed regulator 61 sets asignal equal to the maximum speed to the higher of the two maximum speedsignals. Alternatively, if sensor 57 undergoes a state transition, thelogic circuit sets the limited maximum speed to the lower of the twomaximum speeds. The actual setting of this speed may be done in a numberof different ways depending on the exact structure of the motorregulator 60 and speed regulator 61. For example, if the speed regulatoremploys an analog comparator to compare the user-selected speed to themotor speed, the logic circuit could selectively apply an analog signalof selected magnitude to the comparator based on the output of sensor 44and which one of sensors 53 or 57 underwent a state change.Alternatively, an intermediate output from the logic circuit, based onthe same three inputs would be a digital signal representative of theuser-selected speed. This signal would be converted to an analog signalbefore being applied to the comparator.

[0080] In other versions of the invention, the digital signalrepresentative of user-selected speed may be compared to a digitalversion of motor speed in order to provide the requisite feedback signalrequired to ensure proper operation of the motor.

[0081] In these versions, as well as other versions, of the invention, aNOVRAM may be provided that contains data describing selected limitedmaximum speed or speeds of the motor. In these versions of the inventionthese data are compared to the actual speed of the motor to ensure thatthe motor runs at a limited maximum speed less than the no load speed.Also, these data may be used as input variables to determine the userselected speed in combination with the signal that indicates the extentto which the surgeon depressed the tool control member. In versions ofthe invention in which the motor regulator components are primarilydigital components, the data read from the NOVRAM may be processeddigitally. Alternatively, the data may be converted into a set of analogsignals each of which represents a particular limited maximum speed.

[0082] An advantage of providing the limited maximum speed data in aNOVRAM is that data representing different limited maximum speeds can bestored in different NOVRAMs. Thus, a base unit can be provided that hasa motor that runs at a very high speed. Then, during the assemblyprocess, a NOVRAM with customer-specific limited maximum speeds can beinstalled to complete assembly of the completed tool 20. An advantage ofthis arrangement is that it reduces the number of different parts themanufacturer has to have available in order to provide tools that havedifferent limited maximum speeds.

[0083] Similarly, it should be recognized that resistor 182 that formspart of the limited maximum speed voltage divider may not always be asingle resistor. For purposes of manufacturing a set of series and/orparallel connected resistors may be provided. Then as part of theassembly process, the signal present at the junction of resistor 178 anddiode 180 is empirically set to ensure that the motor runs at theappropriate limited maximum speed. Once this signal is determined,jumpers across the resistors forming resistor 182 are appropriatelyinstalled or removed to ensure that these resistors collectively havethe appropriate resistance to cause to ensure that the output signalapplied to the motor regulator 60 causes the motor to operate at theappropriate speed and does not exceed the desired limited maximum speed.An advantage of providing a set of resistors to form resistor 182 isthat an automated wiring machine can perform the signal calibration andresistor installation/removal.

[0084] It should likewise be understood that some versions of theinvention may include a combination of the above described mechanicaland electric assemblies that regulate speed and offer the maximum speedselect trigger functions of this invention.

[0085] Also, in other versions of the invention, the speed regulator 61may not engage in closed loop regulation of motor speed that holds themotor speed constant as the load applied to the motor varies. In someversions of the invention, the motor regulator 60 and speed regulator 61may be configured so as to regulate the motor speed based on threeinputs: user-selected speed; motor speed; and load applied to the motor.

[0086] This type of speed control is depicted in FIG. 10. Here, linesegment of 188 depicts a speed/torque plot that represents how the motorregulator 60 and speed regulator 61 are configured so that, as the motorstarts to develop torque the maximum speed undergoes a slight increasebefore it starts to fall. In still other versions of the invention, themotor regulator and speed regulator may be configured, so that, asdepicted by line segment 189, as the motor starts to develop torquethere is initially a slight drop in motor speed until, the overall poweravailable to drive the handpiece limits motor speed for the amount oftorque that is produced.

[0087] Moreover, the actual components forming alternative versions ofthis invention may be different from what has been described. Forexample, there is no requirement that all versions of the invention havethe trigger, carriage and magnet position sensor assemblies of thedescribed version of the invention. In an alternative version of theinvention, the trigger, or other user actuated control member, may beconnected to a wiper of a potentiometer internal to the housing 22 thatis part of the motor regulator 60. In these versions of the invention,the speed limiting assembly may comprise a mechanical stop that limitsthe control member from being placed in a position in which the memberplaces the wiper in full speed, no load speed, setting. In the abovetype of assembly, there is a 1:1 correlation between the movement of thecontrol member and the wiper. In an alternative version of theinvention, the drive member between these components may not cause thisdirect motion. In these versions of the invention, the drive member,like leg 88 of outer shaft 84, may be configured to inhibit the extentto which the displacement of the control member by the surgeon resultsin the displacement of the potentiometer wiper to the full speed, noload speed, position.

[0088] The foregoing version of the invention can still be provided witha limited maximum speed speed select feature. For example, if thetrigger actuates a wiper, the rotational position of the trigger may beused to open/close a switch that establishes the resistance of a voltagedivider from which a speed signal or a modified form of the speed signalis applied to the motor regulator and speed regulator.

[0089] Also, from the above, it should be recognized that the structureof the control member actuated by the surgeon may vary from what hasbeen described. In not all versions of the invention is this controlmember a depressible trigger. In some versions of the invention, thecontrol member may be a lever switch that is pivotally connected to thehandpiece housing. In still other versions of the invention, the controlmember may comprise one or more manually actuated electrical switchesthat are mounted to the outer surface of the handpiece housing. In theseversions of the invention, the speed limiting assembly has componentsinternal to the motor regulator and speed regulator that preventoperation of the motor above a maximum speed that is less than the noload speed.

[0090] Also, in some versions of the invention, it may be possible toplace the trigger in three or more orientations so as to establish threeor more maximum operating rates for the associated power generatingunit.

[0091] Similarly, it should be recognized that the control assembly ofthis invention need not always include a single control member that isboth set to establish the limited maximum speed and the surgeon selectedspeed. In some versions of the invention, two control members may beprovided. For example, a first control member may be employed toestablish the limited maximum speed and the second control member isused to establish the surgeon selected speed. In a mechanical version ofthis embodiment of this invention, the first control member may be alever or a screw device that limits the extent to which the secondcontrol member can be physically displaced. In an electrical version ofthe invention, the positions of the first and second control members areconverted into electrical signals. Based on the positions of thesecomponents the motor regulator both sets the surgeon desired speed forthe motor and prevents the motor from being driven above the selectedlimited maximum speed.

[0092] Likewise, it should be understood that other means than sensorsconfigured to measure magnetic field strength may be employed as thecontrol member orientation and/or position detecting sensor of thisinvention. As mentioned above, a potentiometer may function as a sensorthat monitors control member position. One or more contact switches maybe employed as the sensing components that provide signalsrepresentative of control member orientation. Specifically, the controlmember is connected to the microswitch(es) to open/close themicroswitch(es) depending on the orientation of the microswitch.

[0093] In still other versions of the invention, the trigger assemblymay include optical sensors. In these versions of the invention, eachsensed component of the trigger assembly can comprise an always on LED.The complementary sensor is a light sensitive photodiode orphototransistor. Between the LED and sensor is an adjustable shutter.The size of the shutter opening is set mechanically by the trigger as afunction of trigger position. Thus, the amount of light that passesthrough the shutter is a function of trigger position. The photosensorthus generates an output signal representative of trigger position.

[0094] Alternatively, in some versions of the invention, one or moresensors may perform the function of both indicating the orientation ofthe control member and the extent to which it is displaced. For example,in some versions of the invention, as depicted in FIG. 11, there may bejust two magnets 42 and 46 and complementary sensors, 190 and 192,respectively. When the trigger is in a first orientation and depressed,only magnet 42 is moved. The movement of this single magnet 42 isdetected by the complementary sensor 190, hereinafter, the high speedsensor. In response to the change in signal state from the high speedsensor 160, the speed regulator internal to the motor regulator 60 acauses the motor to run within a first speed range up to a first maximumspeed. When slower speed tool operation is desired, the trigger 38, aspreviously described is reset to the low speed operation. Then, when thetrigger is depressed, only a second one of the magnets, magnet 46, ismoved. The complementary sensor 192, hereinafter the low speed sensor,detects this displacement. In response to the state change of the outputsignal from the low speed sensor 192 the speed regulator causes themotor to run within a second speed range up to a second maximum speed.Again, independent potentiometers with wipers that are independentlydisplaced as a function of trigger position could perform the abovedescribed dual sensing function.

[0095] Similarly, it should be understood that the electrical circuitryemployed to apply the energization signals to the motor may be differentfrom what has been described and incorporated herein by reference. Anyanalog, digital and/or combined analog or digital motor controller thatmonitors motor speed, receives a signal representative of the userselected speed and, based on these two inputs, applies the energizationsignals to the motor to cause it to run at the user speed, may beincorporated into the powered surgical tool of this invention.

[0096] Thus, it is the object of the appended claims to cover all suchmodifications and variations that come within the true spirit and scopeof this invention.

What is claimed is:
 1. A powered surgical saw, said saw including: ahandpiece; a motor disposed in said handpiece, said motor having arotating shaft and configured to rotate the shaft at a variable speed inresponse to a variable energization signal wherein said motor has a noload speed; a linkage assembly mounted to said handpiece and connectedto said motor shaft for converting the rotary movement of said motorshaft to a back-and-forth movement; a coupling assembly mounted to saidhandpiece and connected to said linkage assembly to engage inback-and-forth movement in response to actuation of said linkageassembly by said motor shaft, said coupling assembly constructed toremovably receive a saw blade so that the saw blade engages inback-and-forth movement with said coupling assembly; a battery connectedattached to said handpiece to provide energization power to said motor;a user-actuated control member moveably mounted to said handpiece, saidcontrol member having an initial position and a final position and aplurality of user-selected intermediate positions between the initialand final positions, each said position being representative of a userselected motor speed; and a speed regulator mounted to said handpiece,said speed regulator being connected to: said control member to monitorthe movement of said control member; said battery; and to said motor forapplying the energization signal to said motor and for monitoring theshaft speed, said speed regulator configured to, based on the movementof said control member and the motor speed, apply the energizationsignal to said motor so that said operates at a speed based on theposition of said control member as the load applied to the motor varies;and a speed limiting assembly integral with at least one of said controlmember or said speed regulator, wherein said speed limiting assembly isconfigured to limit the speed of said motor so that, when said controlmember is in the final position, said speed regulator causes said motorto run at a maximum speed that is less than the no load speed.
 2. Thepowered surgical saw of claim 1, wherein said speed limiting assembly isassociated with said control member.
 3. The powered surgical saw ofclaim 2, wherein: said control member has a full speed position; saidspeed regulator is configured so that when said control member is in thefull speed position, said speed regulator causes said motor to run atthe no load speed; and said speed limiting assembly includes amechanical member connected to said handpiece positioned adjacent saidcontrol member so as to prevent said control member from being displacedfrom the final position to the full speed position.
 4. The poweredsurgical saw of claim 2, wherein: said control member is part of atrigger assembly and said trigger assembly further includes a moveablesensed element internal to said handpiece, wherein said sensed elementis moveable from a first position to a second position; said speedregulator includes a sensor configured to monitor the movement of saidsensed element and to regulate the energization of said motor so that:when said sensed element is in the first position, the motor is actuatedto run at a slow speed; when said sensed element is in the secondposition, the motor is actuated to run at the no load speed; and, whenthe sensed element is in an intermediate position between the first andsecond positions, the motor is actuated to run at an intermediate speedbetween the slow speed and the no load speed; and said control memberincludes a leg positioned adjacent said sensed element to displace saidsensed element upon movement of said control member and said leg isshaped so that, when said control member is moved to the final position,said leg displaces said sensed element to one of the intermediatepositions located between the first and second sensed element positions.5. The powered surgical saw of claim 1, wherein said speed limitingassembly is associated with said speed regulator.
 6. The poweredsurgical saw of claim 5, wherein: said speed regulator includes a sensorconfigured to monitor the position of said control member, said sensorconfigured to generate a variable speed signal as a function of theposition of said control member wherein when said control member is inthe second limit position, said sensor generates a full speed speedsignal; said speed limiting assembly comprises a signal attenuatorconnected to said sensor for receiving said speed signal and producing amodified speed signal based on said speed signal; and said speedregulator is further configured to receive the modified speed signal andcause said motor to operate at a motor speed that is a function of themodified speed signal, wherein based on the modified speed signalreceived when said sensor produces the full speed speed signal, saidspeed regulator causes said motor to run at the maximum motor speed. 7.The powered surgical tool of claim 1, wherein said speed regulator isconfigured to hold the motor speed at a constant speed as a function ofmovement of said control member when the load applied to said motorvaries.
 8. A powered surgical tool comprising: a handpiece; a variablespeed motor disposed in said handpiece, said motor being configured tooperate at a select speed in response to the application of a selectactuation signal to said motor; a coupling assembly moveably connectedto said handpiece for removably receiving a cutting accessory; a linkageassembly extending between said motor and said coupling assembly fortransferring the rotary motion developed by said motor to said couplingassembly so that, in response to actuation of said motor, said couplingassembly and the cutting accessory attached to said coupling assemblyengage in motion; a battery connected to said handpiece for supplyingelectrical energy to said motor; a control assembly attached to saidhandpiece; said control assembly including: a user-actuated controlmember moveably attached to said handpiece; a sensed member connected tosaid control member to move upon displacement of said control member,said sensed member having a first limit position, a second limitposition and being selectively positionable between said limitpositions; and a stop assembly associated with said control memberpositioned to restrict movement of said sensed member so that saidmember is blocked from moving to the sensed member second limitposition; a motor regulator, said motor regulator connected to saidmotor and said battery for selectively applying the actuation signal tosaid motor, said motor regulator being configured to apply the actuationsignal to said motor so that said motor can operate at speeds up to a noload speed; a speed regulator integral with said motor regulator, saidspeed regulator connected to said motor to monitor the speed of saidmotor, said speed regulator including a sensing assembly for monitoringthe displacement of said sensed member, said sensing assembly generatinga user speed signal representative of user selected speed based on thedisplacement of said sensed member, and said speed regulator isconfigured to, based on the movement of the sensed element and motorspeed, control the application of the actuation signal to said motor bysaid motor regulator as the load applied to said motor varies so thatsaid motor runs at a user selected speed and is further configured sothat, when sensed member moves in the direction of the second limitposition, said speed regulator causes said motor to run at a maximumspeed, the maximum speed being less than the motor no load speed.
 9. Thepowered surgical tool of claim 8, wherein said stop assembly includes amember attached to said handpiece that is positioned to abut saidcontrol member when said control member is moved to displace said sensedmember in the second limit position. 10 The powered surgical tool ofclaim 7, wherein: said control member and said sensed member areseparate, independently moveable components, and said sensed member isdisposed in said handpiece; and said control member includes a driverdisposed in said handpiece, said driver is connected to said sensedmember to move said sensed member upon displacement of said controlmember and said drive is connected to said sensed member so thatcomplete displacement of said control member does not result indisplacement of said sensed member from the sensed member first limitposition to the sensed member second limit position.
 11. The poweredsurgical tool of claim 9, wherein said control member driver is a legpositioned to abut said sensed member upon displacement of said driverand said leg is shaped so that the complete displacement of said controlmember does not result in said leg displacing said sensed member to thesensed member second limit position.
 12. A powered surgical toolcomprising: a handpiece; a variable speed motor disposed in saidhandpiece, said motor being configured to operate at a select speed inresponse to the application of a select actuation signal to said motor,said motor having a no load speed; a coupling assembly moveablyconnected to said handpiece for removably receiving a cutting accessory;a linkage assembly extending between said motor and said couplingassembly for transferring the rotary motion developed by said motor tosaid coupling assembly so that, in response to actuation of said motor,said coupling assembly and the cutting accessory attached to saidcoupling assembly engage in motion; a battery connected to saidhandpiece for supplying electrical energy to said motor; a controlmember moveably attached to said handpiece, said control member having afirst limit position, a second limit position and a plurality ofintermediate positions between the limit positions, and a motorregulator disposed in said handpiece, said motor regulator connected to:said battery; said motor for applying the actuation signal to said motorand for monitoring the speed of said motor; and to monitor the positionof said control member, said motor regulator being configured to, basedon the position of said control member and the speed of said motor,regulate the application of the actuation signal to said motor so thatsaid motor runs at a select speed based on the position of said controlmember and, wherein the speed of said motor is increased as said controlmember moves from the first limit position towards the second limitposition and, when said control member is in a second limit position,said motor regulator applies the actuation signal to said motor so thatsaid motor runs at a maximum speed, the maximum speed being less thanthe motor no load speed.
 13. The powered surgical tool of claim 12,wherein said motor regulator includes: a speed regulator internal tosaid motor regulator for regulating the application of the actuationsignals to said motor so that said motor can operate at variable speedsup to the no load speed, said speed regulator being connected to saidmotor for monitoring the speed of said motor and receiving a speedsignal as an indication of user selected speed for the motor and beingconfigured to control the application of the actuation signal to saidmotor, wherein, based on the speed signal, said speed regulator cancause said motor to operate at the no load speed; a sensor circuit thatmonitors the position of said control member, and said sensor signalgenerates a variable sensor signal as a function of the position of saidcontrol member; a speed limit circuit connected to said sensor circuitfor receiving said sensor signal that, as a function of the sensorsignal, produces the speed signal for application to said speedregulator, and is configured to produce, at a maximum, a speed signalthat indicates said motor is to be operated at the maximum speed. 14.The powered surgical tool of claim 13, wherein said sensor is a magneticfield sensor.
 15. The powered surgical tool of claim 13, wherein saidspeed limit circuit is a voltage divider to which said sensor signal isapplied.
 16. A powered surgical tool, said tool comprising: a handpiece;a power generating unit disposed in said handpiece, said powergenerating unit configured to generate a variable amount of power acoupling assembly attached to said handpiece, said coupling assemblyconfigured to releasably receive a cutting accessory and transfer thepower generated by said power generating unit to said cutting accessory;a control member moveably attached to said handpiece, wherein saidcontrol member is attached to said handpiece to be selectively placed ina first or second orientation relative to a reference point on saidhandpiece and so that when in the first or second orientation, at leasta section of said control member is able to be selectively positionedrelative to the reference point; a sensor assembly disposed in saidhandpiece, said sensor assembly including: at least one first sensorconfigured to monitor the orientation of said control member thatgenerates a first sensor output signal representative of the orientationof said control member; and a second sensor configured to monitor themovement of said control member relative to the reference point thatgenerates a second sensor signal representative of the relative positionof said control member; and a power regulator connected to said sensorassembly to receive the first and second sensor signals and to saidpower generating unit for regulating the amount of power generated bysaid power generating unit, said power regulator being configured sothat: when the first and second sensors indicate that said controlmember is in the first orientation relative to the reference point andin a first position relative to the reference point, said powerregulator causes said power generating unit to produce a first amount ofpower; and when the first and second sensors indicate that said controlmember is in the second orientation relative to the reference point andin the first position relative to the reference point, said powerregulator causes said power generating unit to produce a second amountof power that is different from the first amount of power.
 17. Thepowered surgical tool of claim 16, wherein: said power generating unitis a variable speed motor; and said power regulator is a speed regulatorthat is connected to said motor for regulating the speed of said motor,and is configured so that: when the first and second sensors indicatethat said control member is in the first orientation relative to thereference point and in a first position relative to the reference point,said speed regulator causes said motor to run at a first speed; and whenthe first and second sensors indicate that said control member is in thesecond orientation relative to the reference point and in the firstposition relative to the reference point, said speed regulator causessaid motor to run at a second speed, the second speed being differentfrom said first speed.
 18. The powered surgical tool of claim 16,wherein: said control member is rotatably attached to said handpiece andis further attached to said handpiece so that at least a portion of saidcontrol member is moveable so as to be selectively positionable relativeto the handpiece reference point; and said sensor assembly first sensoris configured to monitor the rotation orientation of said control memberrelative to said handpiece.
 19. The powered surgical tool of claim 16,wherein: said control member is rotatably attached to said handpiece andis further attached to said handpiece so as to be selectively retractedor extended relative to said handpiece; said sensor assembly firstsensor is configured to monitor the rotational orientation of saidcontrol member relative to said handpiece; and said sensor assemblysecond sensor is configured to monitor the extent to which said controlmember is retracted/extended relative to said handpiece.
 20. The poweredsurgical tool of claim 16, wherein: said first sensor includes: firstand second carriages that are disposed in said handpiece and areindependently moveable; a first linkage member attached to said controlmember to move said first carriage when said control member is in thefirst orientation and said control member is positioned relative to thehandpiece reference point; and a second linkage member attached to saidcontrol member to move said second carriage when said control member isin the second orientation and said control member is positioned relativeto the handpiece reference point; wherein, said first sensor linkagemembers are configured so that: when said control member is in the firstorientation and is moved to the first position relative to the handpiecereference point, said first carriage is displaced a first distance and,when said control member is in the second orientation and is moved tothe first position relative to the handpiece reference point, saidsecond carriage is displaced a second distance, the second distancebeing different from the first distance; and said second sensor includesa third carriage that is moveably disposed in said handpiece and saidfirst and second carriages are positioned to displace said thirdcarriage, said first carriage being able to displace said third carriagea distance proportional to the distance said first carriage is displacedand second carriage being able to displace said third carriage adistance proportional to the distance said second carriage is displaced.21. The powered surgical tool of claim 16, wherein said first sensorincludes: first and second carriages that are disposed in said handpieceand are independently moveable; a first linkage member attached to saidcontrol member to move said first carriage when said control member isin the first orientation and said control member is positioned relativeto the handpiece reference point; a second linkage member attached tosaid control member to move said second carriage when said controlmember is in the second orientation and said control member ispositioned relative to the handpiece reference point; and first andsecond carriage sensors, said first carriage sensor configured tomonitor the movement of said first carriage and to generate a firstcarriage signal representative of the displacement of said firstcarriage and said second carriage configured to monitor the movement ofsaid second carriage and to generate a second carriage signalrepresentative of the displacement of said second carriage, wherein thefirst and second carriage signals collectively form the first sensorsignal.
 22. The powered surgical tool of claim 16, wherein said firstand second sensors are separate components.
 23. The powered surgicaltool of claim 16, wherein at least one of said first or second sensorsis configured to monitor magnetic field strength.
 24. The poweredsurgical tool of claim 16, wherein: said first sensor and said secondsensor collectively comprise a first sensing unit and a second sensingunit; said first sensing unit is configured to generate a variable firstsensing unit signal representative of the position of said controlmember relative to the handpiece reference point when said controlmember is in the first orientation; said second unit is configured togenerate a variable second sensing unit signal representative of theposition of said control member relative to the handpiece referencepoint when said control member is in the second orientation so that thefirst and second sensing unit signals collectively function as saidfirst and second sensor signals.
 25. The powered surgical tool of claim24, wherein said first and second sensing units are configured tomeasure magnetic field strength.